Signal generators have been known which transmit a test signal of a communication scheme corresponding to a wireless communication device to the wireless communication device in order to test the wireless communication device. For example, there is a signal generator which stores a baseband signal corresponding to the test signal as digital waveform data in a memory unit thereof, repeatedly outputs the stored waveform data, performs D/A conversion on the waveform data, performs frequency conversion on the converted signal, and outputs the frequency-converted signal as an RF test signal.
In the signal generator, since the capacity of the memory unit is limited, the length of the waveform data is finite. In some cases, it is difficult to freely change the length of the waveform data, for example, since the test conditions for the wireless communication device are defined by a standard. Therefore, in the signal generator according to the related art, a phenomenon in which the phase is discontinuous in a connection portion between the head and tail of the waveform data which is repeatedly output occurs. In this case, there is a concern that spurious emissions will occur at the point where the phase is discontinuous and wireless communication will be asynchronous, which makes it difficult to normally test the wireless communication device.
FIG. 13 is a conceptual diagram illustrating the phenomenon. FIG. 13 shows a waveform when waveform data W including M sample data items D1 to DM is repeatedly output three times and is D/A-converted. Since there is a large difference between the phase of the first sample data item D1 and the phase of the last sample data item DM in the waveform data W, the phase of the D/A-converted waveform is discontinuous in a connection portion between the first repeated waveform data and the second repeated waveform data and a connection portion between the second repeated waveform data and the third repeated waveform data.
In order to solve the problems, an arbitrary waveform signal generating device has been proposed which generates an FSK (Frequency Shift Keying) signal with a waveform pattern in which the phase is continuous in the connection portion (for example, see Patent Document 1). The arbitrary waveform signal generating device includes a digital data generator that repeatedly outputs a PN (Pseudo-Noise) signal and correction means that separately adds a correction value to each bit of the output data of the digital data generator, and can generate an FSK signal in which the phase is continuous in the connection portion.